Refactor module structure #793

Job	Run time
cargo clippy (android) (armv7-linux-androideabi)	44s
cargo check (msrv) (android) (armv7-linux-androideabi)	18s
cargo clippy (android) (aarch64-linux-android)	30s
cargo clippy (windows-latest)	26s
cargo check (msrv) (windows-latest)	19s
cargo check (msrv) (android) (aarch64-linux-android)	33s
cargo clippy (android) (x86_64-linux-android)	37s
cargo clippy (macos-latest)	25s
cargo check (msrv) (android) (x86_64-linux-android)	32s
cargo check (msrv) (macos-latest)	19s
cargo clippy (ubuntu-latest)	27s
cargo check (msrv) (ubuntu-latest)	15s
cargo doc (windows-latest)	18s
formatting	10s
cargo test (windows-latest)	23s
typos	6s
cargo test (macos-latest)	23s
cargo doc (macos-latest)	20s
cargo test (ubuntu-latest)	20s
cargo doc (ubuntu-latest)	16s
	7m 41s

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